The use of magnetoresistors (MRs) and Hall devices as position sensors is well known in the art. For example, a magnetically biased differential MR sensor may be used to sense angular position of a rotating toothed wheel, as for example exemplified by U.S. Pat. Nos. 4,835,467, 5,731,702, and 5,754,042.
Single element magnetic field sensors composed of, for example, an indium antimonide or indium arsenide epitaxial film strip supported on, for example, a monocrystalline elemental semiconductor substrate, are also known. The indium antimonide or indium arsenide film is, for example, either directly on the elemental semiconductor substrate or on an intermediate film that has a higher resistivity than that of silicon. A conductive contact is located at either end of the epitaxial film, and a plurality of metallic (gold) shorting bars are on, and regularly spaced along, the epitaxial film. Examples thereof are exemplified by U.S. Pat. Nos. 5,153,557, 5,184,106 and 5,491,461.
Many kinds of measurements cannot be performed with common magnetic sensors comprising a single or dual sensing element. The most common magnetic sensing element, the Hall sensor, does not quite fit the requirements for an array. Being a 4-terminal device complicates immensely the array connections. Furthermore, its low output signal would mandate the use of an integrated amplifier for each sensing element increasing the die size and its cost. However, compound semiconductor MRs, such as those manufactured from InSb, InAs, etc are simply two-terminal resistors with a high magnetic sensitivity and thus, are very suitable for the construction of single die MR arrays (in most cases one terminal of all the MR elements can be common).
Ultimately, such MR arrays could be integrated on the same die with appropriate processing circuitry. For example, if the MR array was fabricated on a Si substrate then the processing circuitry would be also Si based. For higher operating temperatures, silicon-on-insulator (SOI) could be used. A potentially lower cost alternative to the SOI approach would be to take advantage of the fact that MRs are currently fabricated on GaAs, a high temperature semiconductor, and thus, to fabricate the integrated processing circuitry from GaAs (or related InP) using HBT (Heterojunction Bipolar Transistor) or HEMT (High Electron Mobility Transistor) structures. This technology is now easily available and inexpensive through the explosive growth of the cellular phone industry.
Accordingly, what remains needed is a compact and inexpensive die having at lest one array of magnetic sensing elements and configured so as to produce a variety of array geometries suitable for specialized sensing schemes wherein an array is defined as having three or more rows of MR elements.